Tuning fork generator



May 16, 1933. A. L. MATTE TUNING FORK GENERATOR Filed Jun 16, 1928 ATTORNEY Patented Niay l6,

UNITED STATES PATENT o -"rlca ANDREW L. MATTE, OF SUMMIT, NEW JERSEY, ASSIGNOR TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK TUNING FORK GENERATOR Application filed June 16, 1928. Serial No. 286,042.

This invention relates to tuning forks and the density of the flux threading the genertuning fork generators, and more particularating coil. 1y to arrangements for producing current of While this invention will be pointed out the frequency of vibration of a tuning fork with particularity in the appended claims, 5 or of some harmonic of its frequency of vibrathe invention itself, both as to its further 56 tion objects and features will be better understood In general, the vibration of a tuning fork from the detailed description hereinafter may be made to generate an alternating curfollowing when read in connection with the rent in two distinct ways. First, the vibraaccompanying drawing, in which Figure 1 tion of the tuning fork may be made to shows how the number of effective turns of a 00 change the reluctance of a magnetic path or coil of wire may be periodically changed; circuit to thereby generate an electromotive Fig. 2 shows how the flux threadin a 0011 of force in a coil overwound on some portion of wire may be periodically changef; Figs. 3 this magnetic path or .circuit. Second, the and 4.- show how to produce an alternating flux of. a magnetic path or circuit may remain current from a tuning fork energized from a 66 virtually constant; yet the fork may be made local source, so arranged that the driving flux to vibrate so that the change in the position may have substantially no effect upon the cirof its tines or prongs may divert some of the cuit in which the current is generated; Fig. 5 flux from a number of turns of the coil in shows another embodiment of an electrically which an electromotive force is to be generdriven tuning fork generator for rendering 7 ated. The difference between these two the effect of the driving flux substantially methods will be readily apparent if one re-' negligible in the circuit producing the ge calls that the electromotive force generated erated current; and Fig. 6 represents anwhen a coil is threaded by a magnetic field other arrangement of an electrical driven tunis dependent upon the rate of change of the ing fork generator regeneratively connected 7 linkages formed by the turns of the coil and to a vacuum tube system. the enclosed lines of magnetic induction. Referring to Fig. 1 of the drawing, there Thus, an electromotive force may be produced is shown a tuning fork F having two tines or .either by changing the amount of flux enprongs P and P The tuning fork may be closed by a given number of turns of wire 01 mounted very solidly ona rigid, heavy base 80 bychanging the number of turns of mm onwhich is supported on a soft, diffused bed closlng glven number of 111195 of'magnetlc such as may be provided by pads of rubber.

induction. The principles underlying the This f k may be made fe bl f -ditwo methQds enumeliated h l b 3 be nary soft steel although it will be clear that employed 1n connection w1th the lnventlon to it may be made of any Well known magnetic be subsequently described. One of the Primary objects ofthis invention 25 3;; 252 62151137 mamtamed m mecham is to generate an alternating current by the A coil of Wire W1 wound on a core of iron' t' no t' n of a tunin fork the tunin 0 fgi' k behi :lbtrically drive n. g Is placed .between h tmes or prongs P1 90 Anothel; Object of this invention is to and P a considerable dlstance away from the "ent'the electrical driving means of the tanfree ends of these tmes P ing fork generating arrangement from afl'ectm a may flow through the F g 1 ing or-interfering with the generating action. 15 p h y local Source of dll'ect q Still another object of this invention is to Such as 15 deslgpated as 1' 011 mln l f 95 generate alternating electromotive forces by the Source 1 15 n ed to a Con act D, means of a tuning fork arrangement with While the other terminal of this source is conwhich a generating coil is associated by changnected to the winding W When contact K ing the number of effective turns of the genis closed, current will flow from the source erating coil without-substantially affecting B, through the winding W and over the 1 0 curved portion of the tuning fork F between contact K and the fixed contact D.

The tuning fork F may be started by pulling the prongs P, and P together, i. e., inwardly. After being started, it is driven continuously, the energy for its continuous operation being supplied from the source 13 The contact K provides a make-and-break circuit which periodically interrupts the direct current flowing from the source 13,. Thus, after the prongs P and P have been drawn together, the contact K will be opened so that no current may flow from the source B through the Winding W As these prongs become released, soon the contact K will become closed and current will then flow from the source B through winding W Accordingly, that winding will become excited and its core will become threaded with a dense magnetic field. The prongs P and P will then be attracted, thereby opening the circuit including the source B and the winding W at the contact K. Later, contact K will be closed and another pulse of current will surge through the winding W and the prongs P and P will be attracted, i. e., drawn inwardly again. And, so it continues.

Another core of magnetic material is placed adjacent to the free ends ofthe prongs I and P this core being so spaced from the free ends of these prongs that gaps J and J respectively, are established. A coil of wire W is wound about a portion of the core R adjacent to one of the prongs such as P Coil \V has a plurality of turns of wire so spaced that the length ofthe coil in the direction of its axis is about equal to, and no greater than, the corresponding dimension of the adjacent prong P The winding W is connected to an output circuit S.

As the tuning fork F vibrates, a magnetic field is intermittently established by windin W as hasbeen explained hereinabove. portion of its magnetic flux will flow through the rounded portion of the fork F I (which is at the left of the winding W Another portion of this magnetic field will flow over the prongs P and P and over the iron bar or core R As the fork F vibrates, the magnetic field passing through the bar R will intermittently cut more or less of the turns of wire of coil W In other words, as the fork vi-- brates, the number of effective turns of the winding W, will be continuously change and, consequently, an electromotive force of varying magnitude will be established across its terminals. Consequently, an alternating flow through the circuit S, the frequency of which will have a component equal to the frequency of vibration of the fork F. An alternating current is thus produced by virtue of the continuous change in the number of effective turns of the coil of wire W even though the flux through the core B, were to remain constant.

, maintaining In the usual arrangement for generating an electromotive force by a tuning fork, the flux threading a coil of wire is varied while all of its turns remain in the path of the threading flux. This is illustrated in Fig. 2. In this arrangement, a core .of iron R, is placed between the prongs P and P of the fork F so that gaps J a and J 4 are respectively established between prongs P and P and the ends of the core R The driving circuit for the fork F in vibration after it is started is the same as has been described in connection with the arrangement of Fig. 1, similar reference characters designating similar parts.

As the fork vibrates, the size of the gaps J 3 and J 4 are intermitently changed so that the reluctance of the magnetic circuit, which is threaded by the flux produced by winding W and which passes through the prongs 1 and P is similarly changed. When prongs 1 and P are at their extreme outer positions, i. e., when prongs P and P are the greatest distance apart, the reluctance of the magnetic path is a maximum. On the other hand, when these prongs are at their extreme inner positions, i. e., when these prongs are at their least distance apart, .the reluctance of the magnetic path is a minimum. Since the winding V, is in the path of a periodically varying magnetic ux, the voltage across the terminals of winding W will also vary periodically, this voltage changing from a maximum positive value to a maximum negative value. Accordingly, an rent may flow through the circuit connected to the winding W,. rangement, it will be apparent that while the efiective number of turns of the coil W, remains constant, an alternating current may be produced by virtue of the periodical change of the reluctance of the magnetic circuit threading the winding or coil W,.

In the arangements of Figs. 1 and 2 it will be evident that the wave shape of the electromotive forces produced in windings W and W respectively, are conditioned not only upon the vibration of the fork, but to an equal extent upon the variations of the driving current in winding W Figs. 3 and 4 represent a top view and an end view, respectively, fork arangementfor producing an alternating current by virtue of the vibration of the associated tuning fork. In this arrangement, the flux produced by the electrical driving apparatus is divided and split up into two substantially equal parts which are made to opposeand neutralize each other in the generator windings, thereby preventing fluxes produced by the winding W of the electrical driving aparatus from afiecting the current generating action, as will be apparent from the S wh ch 18 alternating curof an electrically driven tuning the following description. This represents one of the important features of this invention. The circuit arrangement for maintaining the tuning fork in continuous vibration after it,is started, is shown in Fig. 3, in which reference characters similar to those of Fig. 1 have been employed to designate similar parts. The arrangement disclosed by Figs. 3 and 4 is designed to minimize the effect that the flux established by winding W may have upon the nature of the current generated by the-system and flowing through the output circuit S, as suggested herein- I above. Here, two similar yokes of magnetic material R and R are placed adjacent to the prongs P and P of the fork F. The yokes Bran-d R, are so placed with respect to the prongs P and P that gaps J, and J, are established between these yokes and.

A prongs P and gaps J 7 and J B are similarly established between these yokes and prong P The free ends of the prongs P and P will periodically alterthe cross-section and mean length of the effective magnetic path designated in Fig. 4 by the dot-anddash line, thereby periodically changing the reluctance of'this magnetic path.

Coils W, and W, are wound, respectively, on yokes R and R and are connected in series relationship. A battery B connected in series relationship with a choke coil L, supplies current to the windings W and W for their energization, the choke coil L being interposed so as to prevent any alternating current generated by the system from becoming shunted through the battery B A condenser C, preferably of large capacity,

is connected in series with the output circuit S in order that none of the direct current from battery B may reach output circuit S, this condenser, nevertheless, permitting the alternating current generated in windings W and W. to readily flow therethrough. As the fork F vibrates, the reluctance of the magnetic path, including yokes B and it, and gaps J J J and J}; becomes periodically changed, as has been stated hereinabove. Accordingly, electromotive forces are generated in windings W, and W Since these windings are series aiding, the electromotive forces generated thereby will be additive in effect and will result in the transmission of a current of corresponding frequency throughcondenser C to the output circuit S. None of this current can be shunted through the circuit of battery B by virtue of the presence of the choke coil 1L.

The magnetic circuit established by the driving apparatus, i. e., that magnetic cir- '60 cuit produced by winding W shown in Fig.

3, will be substantially without effect upon thevoltages generated by windings W4 and W and therefore without efiect upon the wave shape of the corresponding current transmitted-through the output circuit S.

The magnetic field established by winding W which flows through the prongs P and P also divides between the yokes R, and R Since the gaps J and J 6 are respectively equal in size to gaps J 7 and J the magnetic field established by winding W will pass through these yokes in equal amounts. In other words, the flux densities in the yokes R and R due, to the magnetic field established by winding W are substantially equal and the directions of the fluxes through yokes R and R are in mutually opposite directions. Accordingly, these fluxes will tend to produce mutually neutralizing electromotive forces and thence be substantially without effect upon the generation of the electromitive forces impressed upon circuit S.

Fig. 5 shows another electrically driven tuning fork arrangement for deriving alternating current from the associated continuously vibrating tuning fork, this-arrangement involving a Wheatstone bridge of a magnetic type. Here the core or cores associated with the generating coil are arranged so as to effectively form a magnetic Wheatstone bridge, the generating coil being placed in one of the diagonals of the bridge and the electrical driving apparatus in the other diagonal. Accordingly, the flux produced by the electrical driving apparatus is prevented from interfering with the action of the gencrating coil and this represents another important feature of this invention.

The magnetic apparatus placed between the" prongs P and P of fork F is in the form of a flattened spool, the bases of which are formed by bars R and R and the connecting crosspiece of which is a bar R all of these bars being made of magnetic material. The cross-piece R is shown midway be-. tween bars R and R Gaps J and J bridge the spaces between prongs P and P respectively, and bar R and gaps J and J bridge the spaces between these rongs, respectively, and bar R A winding 6 is wound upon the connecting bar R this winding being supplied with energizing current from a battery B, which is connected in series relationship with choke coil L. Choke coil L prevents generated alternating currents from passing through battery B while condenser C prevents the current from battery B from Howing through the output circuit S. The apparatus employed herein for maintaining the tuning fork in continuous vibration after it is started is the same as has been employed in connection with the arrangement of Fig. 1, the same parts being designated by the same reference characters. 12}

A portion of the magnetic flux derived a from winding W flows through bar R and another portion of this flux flows through bar R Assuming that gaps J and J ad- ]acent to bar R are substantially equal and that gaps J and J adjacent to bar R are also substantially equal, then more flux may, perhaps, thread bar R, than R But since bar R is interposed midway between bars R, and R the ends of bar R; will be at substantially equal magnetic otentials so that substantially no flux may fibw thercthrough. Accordingly, none of the flux derived from winding W will threadbar R and, consequently, no electromotive forces will be established by the terminals of winding W by virtue of the flux from winding W In other.

words, the action of the winding W, in the production of electromotive forces will be substantially unaffected by the driving mechanism and circuit. K

It will be understood that while the termi: nals of bar R are shown in a position midway between the terminals of bars R and R respectively, bar B need not be so placed, for it may be placed in an position with respect to bars R, and R so t at its terminals are at substantially equal magnetic potentials.

As the prongs P and P of the fork F vibrate, gaps J and J as well as gaps J and J Will be periodically-changed in length so that the reluctance of-th'e magnetic path followed by the flux arising from the flow of current from battery B through choke coil L and through winding W will be similarly changed. Accordingly, periodical electromotive forces will be-generated by winding W6 and these periodical electromotive forces will result in an alternating current of corresponding frequency which will become transmitted through condenser C and the output circuit S.

' local source B,.

Fig. 6 shows a regenerative embodiment of an electrically driven tuning fork arrangement for producing alternating current in the manner described hereinabove in connection with Fig.1; Here the flux produced by the electrical driving apparatus isprevented .from threading the core upon which the generating coil is placed and the flux, whose variations are depended upon to produce the desired electromotive force, is provided by a This embodiment includes a vacuum tube system in addition to a tuning fork arrange- "ment. Thevacuum. tube system includes a three-element vacuum tube V, the grid electrode of which is maintained at a suitable negative potential with respect to the cathode by means of the battery B The cathode is heated to an electron-emitting temperature by the flow of current therethrough from a battery B,, a rheostat Z being interposed in series therebetween so that the current from battery B may be roperly regulated. The

movable terminal 0 the rheostat Z is 'connected to the anode of the vacuum tube V through a battery B, and a choke coil L, battery B maintaining the proper operating potential for the anode of the vacuum tube. Part of the output energy of the vacuum tube system is transmitted through a transformer T, the a secondary winding of which is connected to the output circuit S, while the rest of the output energy drives the fork by means of the coil V Condenser C connected in series with the primary winding of transformer T about both cores, the terminals of coil W leading to the movable arm of rheostat Z and lower terminal of the primary winding of transformer "T, respectively.

An iron core or yoke R is U-shaped, so designed and so placed with respect to the free ends of prongs P and P that large surfaces become adjacent to prongs P and P these surfaces being spaced from the free ends of these prongs b gaps J and J respectively. A coil o wire W is wound about the middle section ,of yoke R current for energizing this coil being derived from a battery B Two coils W, and W are also wound about the outer sections of yoke R and are connected in seriesfrelationship between the positive terminal of battery B, and the cathode of vacuum tube V. Eachof the coils V and W includes a number of turns, the overall width of which approximates the width of the prongs P and P res ectively.

When the fork F is in vibration, tiie prongs P and P swing to both sides of thelr nor These coils are connected in series in such a way that the generated voltages will be additive. Consequently, the negative potential of the grid electrode of vacuum tube V with respect to the cathode will be periodically varied, and thereforean alternating current will be produced and transmitted through 115 the primary winding of transformer Some of this alternating current ener will be transmited to the output circuit T he rest of this energy will be su plied to the coil W; so as to-produce peri ic fluxes in the cores R and R in order to maintain the tuning fork F incontinuous vibration.

Equal portions of the fluxes produced by coil W, are transmitted through cores R and R The flux through the prong P willbe' equal to the flux through prong P both being oppositely directed. Accordingl there will be no effect in yoke R as a resu t of the flux generated by winding W It will be understood that the faces of the yoke R which areadjacent to the free ends of prongs P and P are sufiiciently extended so that as the prongs P and P vibrate, there will be substantially no change in the size of the gaps J and J Since these gaps practically determine the reluctance of the magnetic circuit followed by the generator flux produced by the exciting winding VV the voltages generated by coils W and Wm are merely dependent upon changes in the number of their turns intercepted by the flux proceeding from prongs P and? respectively.

It will be understood that while a vacuum tube system has been shown in association with tuning fork F in the arrangement of Fig. 6, the vacuum tube system may be omitted and a driving arrangement of the type shown in connection with Fig. 1 may be substituted therefor to maintain the fork in continuous vibration.

While this invention has been shown in certain particular embodiments merely for the purpose of illustration, it will be understood that the general principles of this invention may be applied to other and widely varied organizations without departing from the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. A tuning fork generator comprising an electrical driving apparatus includinga magnetic circuit, and means for dividing the magnetic circuit into equal and oppositely directed portions for preventing saiclelectrical driving circuit from changing the wave shape of the generated current.

2. A tuning fork generator comprising :means for producing a driving flux, a plurality of windings for producing a generator flux, and magnetic means to substantially shunt said driving flux from the generator windings and thereby prevent the driving flux from affecting the wave shape of the electromotive force generated by the generator flux. k

3. The combination of a tuning fork having a natural vibratory period, means for maintaining the tuning fork continuously in vibration by pulling the prongs together at 4. The combination 'of a mechanically vibrating tuning fork having a predetermined period of vibration, electromagnetic means for continuously -vibrating both prongs of said fork, a stationary coil of wire adjacent "to said fork the efiective number of turns of whichis changed by the vibration of said said natural vibratory period comprising a driving magnet, an electromagnet composed fork, means for preventing the flux of the electromagnetic means from substantially affecting the flux linked with the stationary coil of wire adjacent to said fork, and a circuit including the stationary coil of wire through which will be transmitted cur-- rent of a frequency corresponding to the reltiietermined period of vibration of said or 5. In (an electrically-driven fork- 6, In a regeneratively-driven tuning fork,

generator, means for producing an electromotive force, said means consisting of an lIl'lIIlOV- able generator COll over-wound on a separately excited core which is located adjacent to the ends of the prongs of the tuning fork, and means to periodically divert the generator field from some of the turns of the generator coil. r Y

In testimony whereof, I have signed my name to this specification this 15th day of June 1928.

ANDREW L; MATTE. 

